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Archiver > GENEALOGY-DNA > 2008-10 > 1224083241


From: "Diana Gale Matthiesen" <>
Subject: Re: [DNA] What is a clade?
Date: Wed, 15 Oct 2008 11:07:21 -0400
References: <006601c92e07$1a005d10$6400a8c0@Ken1><f3f05ce80810150353r13ced066y4b891e1a60542144@mail.gmail.com><6ED8813E9B264F4F80074430DA9C24C5@HP><0FED50AB-063F-4CF1-A49B-423256BDD65F@vizachero.com>
In-Reply-To: <0FED50AB-063F-4CF1-A49B-423256BDD65F@vizachero.com>


Vince,

As Richard demonstrated with his excerpt from the "Dictionary of Genetics,"
there are now two definitions of the word "clade." You are using definition 1.
I am using definition 2, which is the original definition of the word as coined
by cladists engaged in cladistics (ca. the 1960s). A technical word with a very
precise meaning now has what I would consider a vernacular meaning, but that's
just my opinion.

Based on current usage, neither of us is "wrong" about the meaning of the word,
"clade," because both definitions are "accepted," if possibly by different
fields of research (e.g., no cladist would accept definition 1). To continue to
argue about which definition is "correct" is pointless, though there's no
question which definition is "original."

I will dispute that the appearance of a second meaning of any word is in any way
"progress," because multiple definitions render a word ambiguous. We now need
to qualify the noun, "clade," with an adjective to distinguish between the two
meanings because we now have "cladistic clades" and "non-cladistic clades."

Your definition, that "a clade is a set of objects that share one (and only one)
common characteristic: a common ancestor," would be a "non-cladistic clade"
because such a clade isn't necessarily holophyletic, nor has it been defined
cladistically. To give a greatly simplified example of the difference...

Your clade could include two brothers and their father, while excluding their
sisters. To be a cladistic clade (to be holophyletic), you would be required to
include the sisters. (Leaving aside entirely how the clade was defined, which
would also be different.)

Diana

> -----Original Message-----
> From: On Behalf Of Vincent Vizachero
> Sent: Wednesday, October 15, 2008 9:05 AM
> To:
> Subject: Re: [DNA] What is a clade?
>
> I don't think the problem is that you know "too much" about
> this topic.
>
> A clade is group of things that descend from a common ancestor.
> Anyone who thinks there is more to it than that has been misled by
> someone.
>
> Put another way, a clade is a set of objects that share one
> (and only
> one) common characteristic: a common ancestor.
>
> If we could simply elevate everyone's understanding to grasp that
> definition, I'd call that progress.
>
> VV
>
>
> On Oct 15, 2008, at 8:27 AM, Diana Gale Matthiesen wrote:
>
> > I agree with you, but we appear to be in a
> > minority. Sometimes you can know too much about something.
>
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